My own accounting python euler problem

[John Machin]

On Nov 8, 8:39 am, vsoler <vicente.so... at gmail.com> wrote:
> In the accounting department I am working for we are from time to time
> confronted to the following problem:
[snip]

> My second question is:
> 2. this time there are also credit notes outstanding, that is,
> invoices with negative amounts. For example,  I=[500, 400, -100, 450,
> 200, 600, -200, 700] and a check Ch=600

How can a credit note be "outstanding"? The accounting department
issues a credit note without recording what invoice it relates to?